It's the Radio Shack Serialization format. Tandy Deskmate was the OS installed on Radio Shack PC compatibles. It included a desktop ticker that could be launched to see what was on sale at Radio Shack that week, updated by calling the Radio Shack BBS. People found they could edit its INI file to add additional news sources, so people could see what files appeared on warez BBSes with the list automatically updated when they called the board, and people even added hacks to add additional 'feeds' like email listing, friends' birthdays, and CompuServe news. Soon it was used for everything, and people started making RSS readers for Windows and Mac as well.
Radio Shack Serialization format. Remember that. Previously Radio shack Deskmate File. (It wasn't RSDF because you could only have 3 character extensions) It went from RDF to RSS when Radio Shack tried to re-introduce the format with GUIDs and such so Radio Shack could control the available sources, but that failed, so they introduced ATOM instead with DeskMate 2.0.
